The present invention relates to an object detector, an object detector system, a display device for object detectors, and a setting device for object detectors.
Object detectors such as photoelectric switches, proximity switches, ultrasonic switches have heretofore been used for detecting the presence or absence of a moving object along production lines in plants (or factories). For example, a photoelectric switch determines the presence or absence of an object by projecting light onto the conveying path of an object and detecting the presence or absence of reflected light or transmitted light from the object.
In a photoelectric switch of a transmitting type, in the case where there is no object to be detected in a sensing region, light emitted from the light-emitting section is received by the light-receiving section. In this case, when the level of light received is equal to or smaller than a predetermined threshold, it is judged that the object is present. On the other hand, in a photoelectric switch of a reflecting type, in the case where there is an object to be detected in the sensing region, light emitted from the emitting section is reflected by the object, and the reflected light is received by the light-receiving section. In this case, when the level of light received exceeds a predetermined threshold, it is judged that the object is present. The sensitivity of the photoelectric switch is adjusted by changing the aforementioned threshold (operative level).
The thus operating photoelectric switches may, in some cases, face the problem that the level of light received is reduced due to such causes as displaced optical axis, stained light-emitting or light-receiving surfaces, or deteriorated performance of the light-emitting element of the light-emitting section. In these cases, it is necessary to re-set the sensitivity by changing the threshold of the photoelectric switch.
To overcome this problem, photoelectric switches of an automatic sensitivity setting type which can set the sensitivity automatically are being developed. Automatic sensitivity setting photoelectric switches sample received light quantities by a control input from an external device and set a threshold based on groups of data obtained by causing a microcomputer or the like to calculate the sampled data.
In the aforementioned automatic sensitivity setting type photoelectric switch, a threshold is automatically set within the photoelectric switch so that the sensitivity of the photoelectric switch becomes proper. However, the operator is not informed of a set threshold, nor can he finely adjust the set threshold so as to match a measuring environment.
On the other hand, some conventional photoelectric switches display the level of light received by using a plurality of light-emitting diodes (LED). However, the operator is not informed of a correct quantity of light received, nor can he be informed of a currently set threshold. Thus, a margin of the quantity of light received with respect to the currently set threshold cannot be recognized. As a result, the operator cannot know the timing at which to re-set the sensitivity, either.
Moreover, in a photoelectric switch system having a plurality of photoelectric switches, a respective threshold must be set for each photoelectric switch. In an automatic sensitivity setting type photoelectric switch system in particular, each photoelectric switch has a threshold automatically set. In this case, the operator is not informed of a threshold set for each photoelectric switch, nor can he be informed of the level of light received of each photoelectric switch correctly, either. Further, he cannot make a fine adjustment of the threshold set for each photoelectric switch so as to match a measuring environment, either.
An object of the present invention is to provide an object detector system including an object detector that allows the operator to be informed of a set threshold or a detected quantity correctly.
Another object of the present invention is to provide an object detector system including an object detector that allows the operator to finely adjust a set threshold.
Still another object of the present invention is to provide a display device for object detectors that can display the threshold or detected quantity of an object detector correctly.
Still another object of the present invention is to provide a setting device for object detectors that can finely adjust the threshold of an object detector.